CONSORT diagram

• From August 2019 to March 2020, we screened 270 patients undergoing CIED procedures.
• A total of 130 participants were randomized.
• One participant was subsequently excluded from the study because their procedure was cancelled after the randomization was performed.
• One further participant, who was randomized to the HFNO group, had their procedure rescheduled to a time that the Research Assistant was not available. As such, this participant received oxygen via standard face mask and TcCO₂ data were not collected.
• Two participants who were randomized to HFNO did not receive this intervention at all during procedures at the discretion of the Anesthesia Assistant, with the rationale that the high flow of oxygen interfered with capnography monitoring.
• For two participants, the TcCO₂ sensor failed to callibrate prior to commencement of the procedure, so they were not able to be included in the analyses for the TcCO₂ outcomes.

Reasons for exclusion from the trial

The total number of exclusions displayed here is not equal to the actual total number of participants not meeting the inclusion criteria (displayed in the CONSORT diagram), as some participants had multiple reasons for exlcusion.

Peak TcCO₂ against baseline

The average difference (95% credible intervals) in peak TcCO₂ between groups was 0.0 mmHg (-1.3, 1.36).

Mean TcCO₂ against baseline

The average difference (95% credible intervals) in mean TcCO₂ between groups was -0.1 mmHg (-1.29, 1.1).

Subgroup analysis for peak TcCO₂

Missing CO₂ measurements

• For two participants, the Sentec VSign 2 sensor failed to calibrate, so these participants were not able to be included in the analyses for the TcCO₂ outcomes.
• For a small number of participants there was a delay in calibration of the Sentec VSign 2 sensor, resulting in a small amount missing data for a period of time at the start of procedures.
• One participant had their procedure rescheduled to a time that the researchers were unavailable. As such, TcCo₂ measured for this participant.

High flow nasal oxygen

Data shown here are for who experienced an oxygen desaturation event (defined as SpO₂ <90%). Hover over a line to highlight a particular sequence.

Facemask oxygen

Data shown here are for who experienced an oxygen desaturation event (defined as SpO₂ <90%). Hover over a line to highlight a particular sequence.

Missing SpO₂ measurements

Routinely collected SpO₂ data were extracted from the Drug Reconciliation and Electronic Monitoring system for this outcome. Missing values at the beginning of these trajectories reflect the time prior to commencement of procedures when patients are getting prepared.

Comfort with the oxygen device

The treatment effect (95% credible intervals) was 1.2 (0.62, 2.22).

Anesthesia Assistant rating for difficulty using the oxygen device

The treatment effect (95% credible intervals) was 0.3 (0.15, 0.82).

Anesthesia Assistant rating for difficulty maintaining oxygenation status

The treatment effect (95% credible intervals) was 0.1 (0.05, 0.32).

Iowa Satisfaction with Anesthesia Scale scores

The treatment effect (95% credible intervals) was 0.0 (-0.34, 0.23).

Oxygen flow rate in litres per minute for each participant

• Participants randomized to the HFNO group received flow rates at 50 litres per minute or higher for the majority of the time.
• One participant who was randomized to receive HFNO had their procedure rescheduled to a time that the Research Assistant was not available. As such, this participant received oxygen via standard face mask.
• Two participants who were randomized to HFNO did not receive this intervention at all during procedures at the discretion of the Anesthesia Assistant, with the rationale that the high flow of oxygen interfered with capnography monitoring.
• Four participants who were randomized to HFNO stopped receiving this intervention at a certain timepoint during procedures at the discretion of the Anesthesia Assistant, with the rationale that the high flow of oxygen interfered with capnography monitoring.

Oxygen flow rate as a proportion of the total time of all procedures

• Participants randomized to the HFNO group received flow rates at 50 litres per minute or higher for the majority of the time.

Oxygen to air ratio for each participant randomized to high flow nasal oxygen

• Most participants randomized to HFNO received an oxygen to air ratio of 50% for their entire procedure.
• The oxygen to air ratio was increased higher than 50% for only a small number of participants, at the discretion of the Anesthesia Assistant to improve oxygenation.
• For participants who were switched to oxygen supplementation via a standard facemask, the oxygen to air ratio was assumed to be 1.0.

Number of times Anesthesia Assistants reported having used high flow nasal oxygen